I looked at the manual online and it looks fairly straightforward.
Live (hot from breaker box) goes to the L connector.
Neutral (to the light fitting) goes to the 1 connector.
Red and black go to your existing switch for local control.
The problem is that you don't appear to have standard wiring for a single switch. UK switches normally have just the live (black, red or white) and neutral (black with a red band, white, red or black) with the green (bare copper or green/yellow) ground / earth tucked away in the back just like yours is. The 3 browns and 3 blues look kinda funky from where I'm sitting, but UK codes is UK codes and subject to change with the wind/weather and it's been a few years since I played with english electric.
Possibly your switch is or was part of a 2 way, 3 way or 4 way lighting circuit - more than one switch operating the same light or lights?
Would wiring it with reverse polarity blow anything inside when the power is switched back on?
Do you have a way to test what is live and what isn't? Or a continuity tester to see what wire goes where?
USA electric is much more relaxed - over here we get to use very old-fashioned toys like wire nuts, fingers and thumbs for testing live wires, and they don't change the colour designations whenever the wind changes direction